Two metal rods, one silver and the other gold, are attached to each other. The f

Question

Two metal rods, one silver and the other gold, are attached to each other. The free end of the silver rod is connected to a steam chamber, with a temperature of 100°C, and the free end of the gold rod to an ice water bath, with a temperature of 0°C. The rods are 5.0 cm long and have a square cross-section, 2.0 cm on a side. How much heat flows through the two rods in 60 s? The thermal conductivity of silver is 417 W/(m*k) and that of gold is 291 W/(m*k). No heat is exchanged between the rods and the surroundings, except at the ends.

Explanation / Answer

rate = kA*temp_diff/l

=> temp_difference = rate*l/KA     (analogus to V = IR)

so both rods are in serise

=> Req = l1/K1A1 + L2/K2A2 = 0.05/(417*0.02*0.02) + 0.05/(291*0.02*0.02) = 0.729

=> rate = 100/0.729 = 137.174 W

=> heat flow in 60 s = rate*time 137.174*60 = 8230.44 Joule Answer

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